Hydroxyl free radical-induced decontamination of airborne spores, viruses and bacteria in a dynamic system

ABSTRACT

A method and apparatus is described for neutralizing airborne pathogens and chemical toxins in ventilated air, and in heating or air conditioning systems. The pathogen-chemical toxin neutralization system is effective against a wide spectrum of pathogens and toxins, it incorporates commercially available components, and it can be readily integrated into commercial HVAC systems where it decontaminates large volumes of ventilated air in real time without any chemical reagents. The system has a flow-through reaction chamber ( 101 ) that contains a UV light source ( 106 ) that emits short intense flashes of broad-spectrum UV light, a source aqueous hydrogen peroxide that can be a reservoir or a hydrogen peroxide generator ( 106 ), and optionally a source of ozone. The interaction of UV light and hydrogen peroxide generates hydroxyl radicals that neutralize pathogens and chemical toxins as they pass through the reaction chamber ( 101 ) in real time. The pathogens that can be neutralized by this system include bacteria, viruses, spores, fungi and parasites.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of prior filed co-pending U.S.Provisional Application Ser. No. 60/438,287, filed Jan. 6, 2003, whichis incorporated herein by reference as if fully set forth herein under35 U.S.C. Section 119(e).

This application is also related to U.S. Ser. No. 10/257,196 filed onOct. 9, 2002 (hereafter “Potember”) which is incorporated herein byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a new, safe, effective method forneutralizing or destroying a wide range of airborne pathogens (spores,bacteria and viruses) and chemical toxins in commercial HVAC airhandling systems.

2. Description of the Related Art

It is critical to develop rapid, effective, and safe (nontoxic and notcorrosive) technologies for neutralizing airborne pathogens and chemicaltoxins to protect civilian and military facilities from a chemical orbiological attack. Within this area, there is a special need to protectdomed stadiums, subways, and enclosed facilities (buildings and commandcenters that may contain extremely sensitive equipment). This effort isa key to eliminate the threat of biological and chemical weapons in theplanning and conduct of US military operations. While no defense canstop an adversary from unleashing such weapons, a sufficiently robustarray of defenses, countermeasures and deterrents will reduce the damageresulting from biological and chemical weapons used in a particularoperation.

There is also a great need to remove airborne pathogens from airhandling systems in hospitals and on airplanes where the transmission ofrespiratory infections in indoor environments represents a major publichealth concern for which engineering alternatives are limited. Evidencefor the dissemination of respiratory diseases inside buildings, andspecifically by ventilation systems, exists in the epidemiological data.The risk to patients of becoming infected with Staphylococcus, one ofthe most common and deadly infections associated with prolonged hospitalstay, is significant.

To accomplish these goals, a pathogen-toxin neutralization technology isneeded that can destroy a wide range of pathogens (spores, bacteria, andviruses) and chemical toxins in air in real time as the air movesthrough an HVAC system without introducing contamination into the airhandling system. The neutralization of airborne biological and chemicaltoxins is a very difficult problem to solve because, to be useful, itmust work in real time, and handle large volumes of moving air.

In Potember, a UV/ozone pathogen neutralization system was disclosedbased on the discovery that irradiating ozone with high intensity, broadspectrum UV light in the presence of water generates highly reactiveozone intermediates and free radicals that destroy a wide range ofairborne pathogens. The ozone intermediates and free radicals were moreeffective at neutralizing pathogens than ozone or UV light alone.Massive amounts of airborne Erwinia herbicola vegetative bacteria andMS2 virus introduced into the UV/ozone system were reduced toundetectable levels. However, while the system was able to destroyapproximately one to two orders of magnitude of extremely high levels ofairborne Bacillus globii spores, an anthrax stimulant, it was not ableto reduce the total population of airborne spores to undetectablelevels. Therefore, there is a need for a pathogen neutralization systemwith increased efficiency for neutralizing airborne bacterial spores inreal time.

The past approaches described in this section could be pursued, but arenot necessarily approaches that have been previously conceived orpursued. Therefore, unless otherwise indicated herein, the approachesdescribed in this section are not prior art to the claims in thisapplication and are not admitted to be prior art by inclusion in thissection.

SUMMARY OF THE INVENTION

A system for neutralizing airborne pathogens or chemical toxins isdisclosed. The system has a flow-through reaction chamber with a chamberair inlet at a first end of the reaction chamber to admit aircontaminated with pathogens, and a chamber air outlet at a second end ofthe reaction chamber to release decontaminated air, and defining betweenthe air inlet and air outlet a passageway. The system further includes asupply of aqueous hydrogen peroxide connected to a conduit forintroducing aqueous hydrogen peroxide into the reaction chamber, and anultraviolet light source for introducing UV light into the reactionchamber.

In an embodiment of this aspect, the aqueous hydrogen peroxide supply isa hydrogen peroxide generator connected to a water supply and a sourceof electricity. In another embodiment, the aqueous hydrogen peroxidesupply is a reservoir of aqueous hydrogen peroxide that can be locatedinside or outside the reaction chamber. In some embodiments, the conduitincludes a nozzle disposed inside the reaction that releases the aqueoushydrogen peroxide as a spray, mist or vapor. To provide additionalsurface area, on which the neutralization process can occur, someembodiments of the system optionally contain a porous matrix such asmetal foam made of aluminum, copper, silver, or metal oxides. In someembodiments, the neutralization system includes an ozone supply inaddition to the aqueous hydrogen peroxide supply and a conduit forintroducing ozone into the reaction chamber that can optionally be anozzle disposed inside the reaction chamber. In some embodiments theozone supply is an ozone generator or a reservoir of ozone. In anotherembodiment, the aqueous hydrogen peroxide supply is connected by aconduit to the ozone supply so that ozone passes from the ozone supplyinto the aqueous hydrogen peroxide supply thereby forming a mixture ofhydrogen peroxide, water and ozone that can be sprayed into the reactionchamber.

In some embodiments of the aspect, the reaction chamber includes a solidsupport that is made of or coated with ozone removal catalysts. Thesolid support can also be made of or coated with compounds that adsorbor neutralize pathogens or chemical toxins or both. In the variousembodiments, the neutralization system is configured for operation in acontinuous mode or is activated upon demand. The system optionallyincludes a fan. Embodiments include an UV light source in the reactionchamber that emits high intensity UV light. In an embodiment of theaspect the UV light has a wavelength in a range from about 100 to about350 nm.

In another aspect of the invention, methods of neutralizing airbornepathogens or chemical toxins include the steps of introducing aircontaminated with pathogens or chemical toxins or both into aflow-through reaction chamber. Aqueous hydrogen peroxide is introducedinto the flow-through reaction chamber to form a mixture of contaminatedair and aqueous hydrogen peroxide. The mixture is irradiated withultraviolet light thereby neutralizing the airborne pathogens orchemical toxins. The decontaminated air is released from the reactionchamber. In another embodiment of this aspect, the method furtherincludes introducing ozone into the reaction chamber to form a mixtureof ozone, contaminated air and aqueous hydrogen peroxide that isirradiated inside the reaction chamber with UV light. In an embodimentof this aspect, a concentration of hydrogen peroxide in the flow throughreaction chamber is maintained at a level in a range from about 1% toabout 50%; in another embodiment the concentration is maintained at alevel in a range from about 1% to about 25%. In some embodiments thatinclude introducing ozone into the reaction chamber, the concentrationof ozone in the reaction chamber is maintained at a level in a range offrom about 0.01 ppm to about 1000 ppm, or in a range from about 0.1 ppm(part per million) to about 1000 ppm.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a block diagram of an embodiment of the UV/H₂O₂ neutralizationsystem having the hydrogen peroxide (H₂O₂) generator 104 disposed insidethe flow-through reaction chamber 101.

FIG. 2 is a block diagram of an embodiment of a UV/H₂O₂/ozoneneutralization system that has an external hydrogen peroxide and ozonesupply 204.

FIG. 3 is a block diagram of an embodiment of the hydrogen peroxidesupply 204A that includes ozone.

FIG. 4 is a block diagram of another embodiment of the hydrogen peroxidesupply 204B that includes ozone.

FIG. 5. Illustrates the pathways for pathogen and chemical toxindestruction and free radical generating chemical reactions that takeplace in the UV/H₂O₂/ozone neutralization system.

FIG. 6 is a block diagram of the UV/H₂O₂/ozone neutralization systemused in Example 2.

FIG. 7 A-F are photographs of plates that were exposed to air going intoand out of the flow-through reaction chamber in experiments designed totest the ability of the UV/H₂O₂/ozone neutralization system toneutralize a large excess of airborne Bacillus globii spores in realtime.

FIG. 8. A-F are photographs of plates that were exposed to air goinginto and out of the flow-through reaction chamber in experimentsdesigned to test the ability of the UV/H₂O₂ neutralization system toneutralize a large excess of airborne Bacillus globii spores in realtime without ozone.

DEFINITIONS

Free radical means intermediate chemical species that contain unpairedelectrons, including hydroxyl ions (OH⁻).

Pathogen means any disease-causing organism including bacteria in thevegetative or spore form, viruses, molds, fingi, and parasites. Pathogenalso means bacterial toxins as defined herein, prions and biologicalweapons as defined herein.

Pathogen-neutralized air means air in which the pathogens have beenreduced neutralized, inactivated, mutated or killed so that they can nolonger reproduce or cause infection.

Decontaminated air means air that has passed through various embodimentsof the neutralization systems of the present invention.

Biological weapons means any pathogen, including those listed herein andalso their DNA or RNA or fragments, that could be introduced into theair or water or put on surfaces.

Bacterial toxin means any part of a bacterium that is toxic to ananimal, including a human.

DETAILED DESCRIPTION

A method and apparatus are described for neutralizing airborne pathogensand chemical toxins in real time in circulating air. In the disclosedembodiments the pathogens and toxins react with free radical hydroxylions (OH⁻) generated by irradiating aqueous hydrogen peroxide (H₂O₂)with broad spectrum, intense UV light in a closed, flow through system,hereafter “the UV/H₂O₂ system.” The UV/H₂O₂ system is designed for usein ventilated air and in heating or air conditioning systems thatcirculate potentially contaminated air. The embodiments are effectiveagainst airborne pathogens including bacteria, viruses, spores, fungi,molds and parasites. The system is also effective in oxidizing airbornechemical toxins, thereby converting potentially deadly compounds toenvironmentally and physiologically benign compounds. Hydrogen peroxidecan be used as the sole source of free radicals or it can be usedtogether with ozone, which also generates highly reactive free radicalsupon irradiation with UV light in a moist environment. When ozone isused with H₂O₂, the system is referred to as “the UV/H₂O₂/ozone system.”Various combinations of UV, H₂O₂ and ozone may be advantageous,depending on the targeted pathogens and chemicals. The invention is notlimited to the described embodiments. In the following description, forthe purposes of explanation, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art that the presentinvention may be practiced without these specific details. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring the present invention.

The destructive action of ozone dissolved in water on microorganisms isknown, particularly on the Escherichia coli (E. Coli), Cryptospondium,Poliovirus and Giardia cysts (including Giardia muris and Giardialamblia). E. Katzenelson and H. I. Shuval, “Studies on the disinfectionof water by ozone: viruses and bacteria”, First International Symposiumon Ozone for Water & Wastewater Treatment, Vol. 1, Rice, R. G., andBrowning, M. E., Eds., Hampson Press, Washington D.C. (1973); W. T.Broadwater, R. C. Hoehn, and P. H. King, “Sensitivity of three selectedbacterial species to ozone”, Appl. Microb. 26:391-393 (1973).

Ozone and UV light have been used either alone or in combination toneutralize pathogens and chemicals in contaminated water (wastewater andwater contaminated with industrial pollution). U.S. Pat. No. 4,156,652,652, U.S. Pat. No. 4,179,616, U.S. Pat. No. 4,204, U.S. Pat. No.4,230,571. More recently, the combination of UV, ozone and hydrogenperoxide has been used in wastewater purification. Clarin, J. et al.,“UV/Ozone/Peroxide Treatment”, published as part of the curriculum forENVE 436, Civil and Environmental Engineering Department, CaliforniaPolytechnic State University (hereafter “Clarin”); Jensen, L., U.S.Patent Application No. 2002/0071793; Peyton, G. R., U.S. Pat. No.5,762,808; Mausgrover et al., U.S. Pat. No. 5,427,693; Zeff et al., U.S.Pat. No. 4,849,114; and Murphy et al., U.S. Pat. No. 6,387,241 B1.Clarin, et al. also reports the use of UV and H₂O₂ without ozone forsterilizing contaminated water. All of these methods require longresidence times to accomplish water sterilization. Murphy et al. furtherdescribe the use of free radicals generated primarily from ozone andhydrogen peroxide to sterilize soil or contaminants on instruments in aclosed chamber, however, very long residence times measured in hours areagain required.

In a study aimed at neutralizing pathogens on surfaces, it was shownthat ozone in the presence of water vapor neutralizes cultured E. coliand Staphylococcus aureus bacteria on the surface of a petri dish.However, this experiment was conducted in a closed system where ozonewas present in concentrations from between 300 and 1500 ppm (part permillion) and exposure times were from 10-480 seconds in duration. Theseconditions therefore do not simulate a situation such as biologicalwarfare where airborne pathogens have been released into a room or abuilding. Moreover, pathogen neutralization was not achieved in realtime, the chamber contained a small volume of stagnant air, and theozone concentrations were very high. J. Kowalski, W. P. Bahnfleth, andT. S. Whittam, Bactericidal Effects of High Airborne OzoneConcentrations on Escherichia coli and Staphylococcus aureus, OzoneScience & Engineering 20:205-221 (1998). Kowalski, et al. suggestedadding UV light to the system to increase toxicity of the ozone,however, this was not tested. The extremely high ozone levels used andthe long residence times in the system are unacceptable for real timedisinfection of pathogen-contaminated air.

In a related application, Potember discloses a UV/ozone airbornepathogen neutralization system that kills airborne pathogens in realtime as the pathogens move with contaminated air through air handlingsystems into which the system is installed. The pathogens are killedprimarily by highly reactive ozone intermediates and free radicals suchas hydroxyl ions, which oxidize critical components in the pathogens; UVlight and ozone also have intrinsic antimicrobial effects. The systemhas a flow-through reaction chamber with a chamber air inlet to admitmoving pathogen-contaminated air, and a chamber air outlet to releasepathogen-neutralized air. A space is defined between the chamber airinlet and outlet that accommodates the passage of moving air through thesystem. The reaction chamber also contains one or more UV light sourcesthat emit high intensity, broad-spectrum UV light from about 250-280nanometers (nm). In this system, water is sprayed into the reactionchamber into which ozone gas is introduced. In the moist environment,ozone reacts with UV light to form free radicals and other intermediatesthat oxidize airborne pathogens thereby neutralizing them.

This UV/ozone system is effective against a wide range of pathogensincluding Bacillus globii spores, vegetative Erwinia herbicola and MS2virus. The intermediates and free radicals, generated in the UV/ozonesystem from the interaction of ozone, water and broad spectrum UV lightare more effective at neutralizing pathogens than either ozone or UVlight alone, which themselves have intrinsic anti-microbial activity.The UV/ozone neutralization system reduced the extremely high level ofairborne vegetative Erwinia herbicola bacteria and bacteriophage MS2virus introduced into the system to undetectable levels. It also killeda very high percentage of airborne Bacillus globii bacteria spores,which are a simulant for Anthrax. Various embodiments of the UV/ozonesystem in Potember killed or neutralized very high levels airbornepathogens, and even more importantly, accomplished this in real time inlarge volumes of moving air. However, while highly effective in killingvery large amounts of airborne Bacillus globii bacteria spores, thesystem was not able to eliminate these spores entirely. Bacterial sporesare particularly difficult to destroy because they can surviveindefinite periods of starvation, desiccation and exposure to toxicchemicals. Resistance is due to the spore being surrounded by twosubstantial structures: (1) the cell wall keeps a spore interior dry,thus preventing damage to DNA, and (2) a coating of 20 proteins shieldsthe spore from harmful molecules. A neutralization technology must bothpenetrate the outer cell wall and destroy critical components of thecell to cause death of the cell or prevent reproduction.

In order to try to increase the efficacy of the UV/ozone pathogenneutralization system against airborne Bacillus globii spores and otherpathogens, a concentration of about 25% aqueous hydrogen peroxide wasintroduced into the reaction chamber together with ozone. Aqueoushydrogen peroxide irradiated by high intensity, broad spectrum UV lightfrom about 150 nm to about 300 nm, particularly from about 250 nm toabout 270 nm) generates highly reactive hydroxyl ions (OH⁻) that arepowerful oxidizing agents. Whereas the original UV/ozone neutralizationsystem killed or neutralized only about one to two orders of magnitudeof a large excess of incoming airborne Bacillus globii spores, theaddition of 25% aqueous hydrogen peroxide to ozone and UV light reducedthe number of airborne spores leaving the system to undetectable levels.This embodiment of the neutralization system including hydrogenperoxide, ozone and UV light (hereafter referred to as “theUV/H₂O₂/ozone system”) is more effective against airborne bacterialspores than the Potember system. These results are discussed in Example2.

Additional experiments were performed to test the efficacy of an evenlower concentration of 15% hydrogen peroxide and UV light on airborneBacillus globii spores, without ozone. It was discovered that the systemwas able to reduce the level of airborne Bacillus globii bacterialspores to undetectable levels in real time as the contaminated aircirculated through the reaction chamber at speeds encountered in atypical HVAC system, using 15% aqueous hydrogen peroxide (H₂O₂) and UVlight alone. These results are reported in Example 3. This embodiment ofthe neutralization system, hereafter “the UV/H₂O₂ system,” was aseffective as the more complicated UV/H₂O₂/ozone system against airbornespores, thus permitting the construction of simpler systems that do notrequire ozone. Experiments have been conducted that neutralize a largeexcess of Bacillus globii spores to undetectable levels in real time inthe UV/H₂O₂ system using as little as 3% aqueous hydrogen peroxide. Thepresent embodiments of the UV/hydrogen peroxide systems neutralizepathogens (or chemical toxins which are discussed below) using UV lightand from about 0.5% to about 50% aqueous hydrogen peroxide, particularlyfrom about 1% to about 15%.

Hydroxyl radicals generated by the reaction of hydrogen peroxide and UVlight, though extremely reactive, have a half-life of approximately 10⁻⁹seconds, therefore producing no harmful byproducts. Embodiments of thepresent invention require no chemical reagents, incorporate commerciallyavailable components, and can be readily integrated into commercial HVACsystems.

Free radical hydroxyl ions are believed to destroy microorganisms byoxidizing constituent elements of the cell walls before penetrating themicroorganisms where they oxidize certain essential elements (e.g.,enzymes, proteins, DNA, RNA). When a large part of the membrane barrieris destroyed, the cells lyse (unbind) resulting in immediateneutralization. Other microorganisms, including viruses, are alsodestroyed by oxidation. Viral DNA is also susceptible to destruction byUV light. It is expected that the free radicals in the present UV/H₂O₂system will destroy any airborne pathogens including bacteria, viruses,fungi, molds, prions and parasites. Airborne bacterial toxins orfragments of toxic bacterial cell walls will also be neutralized by theUV/hydrogen peroxide system.

Biological agents that can be destroyed using embodiments of the UV/H₂O₂system or the UV/H₂O₂/ozone system described herein, and thecorresponding diseases caused by them, are listed in Table 1. Category Alists high-priority agents including organisms that pose a risk tonational security because: they can be easily disseminated ortransmitted from person to person; result in high mortality rates andhave the potential for major public health impact; might cause publicpanic and social disruption; and require special action for publichealth preparedness. Category B lists the second highest priority agentsincluding those that: are moderately easy to disseminate; result inmoderate morbidity rates and low mortality rates; and require specificenhancements to the Center for Disease Control's diagnostic capacity andenhanced disease surveillance. Category C lists the third highestpriority agents including emerging pathogens that: could be engineeredfor mass dissemination in the future because of availability; ease ofproduction and dissemination; and potential for high morbidity andmortality rates and major health impact. TABLE 1 Category A Anthrax(Bacillus anthracis) Botulism (Clostridium botulinum toxin) Plague(Yersinia pestis) Smallpox (variola major) Tularemia (Francisellatularensis) Viral hemorrhagic fevers (filoviruses [e.g., Ebola, Marburg]and arenaviruses [e.g., Lassa, Machupo]) Category B Brucellosis(Brucella species) Epsilon toxin of Clostridium perfringens Food safetythreats (e.g., Salmonella species, Escherichia coli O157:H7, Shigella)Glanders (Burkholderia mallei) Melioidosis (Burkholderia pseudomallei)Psittacosis (Chlamydia psittaci) Q fever (Coxiella burnetii) Ricin toxinfrom Ricinus communis (castor beans) NEW! Staphylococcal enterotoxin BTyphus fever (Rickettsia prowazekii) Viral encephalitis (alphaviruses[e.g., Venezuelan equine encephalitis, eastern equine encephalitis,western equine encephalitis]) Water safety threats (e.g., Vibriocholerae, Cryptosporidium parvum) Category C Emerging infectious diseasethreats such as Nipah virus and hantavirus1. Structural Components

FIG. 1 is an embodiment of a self-contained UV/H₂O₂ system. Thisembodiment has a flow-through reaction chamber 101 that has a chamberair inlet 102 to admit pathogen-contaminated air, and a chamber airoutlet 109 to release pathogen-neutralized air. A space is definedbetween the chamber air inlet and outlet that accommodates the passageof moving air through the reaction chamber. Reaction chamber 101contains one or more UV light sources 106 that emit high intensity,broad-spectrum V light. The size of the reaction chamber, the dimensionsof the air inlet and air outlet, and the number of UV lights can bevaried depending on the volume of air moving through the system.

The reaction chamber 101 contains a hydrogen peroxide generator 104connected to water supply line 103. Aqueous H₂O₂ produced by hydrogenperoxide generator 104 passes through nozzle 105 and into reactionchamber 101 as a spray, fine mist or vapor. The aqueous H₂O₂ reacts withthe UV light provided by UV light source 106 to form hydroxyl freeradicals (OH⁻) 111. In some embodiments, the reaction chamber is linedwith an UV reflective coating or is built of an UV reflective material.

In another embodiment of the UV/H₂O₂ system, an aqueous H₂O₂ supply (atank or reservoir or generator) is disposed outside reaction chamber101, and connected by a supply line to a nozzle disposed inside thereaction chamber 101. If the H₂O₂ in the supply is the desired strength,it is sprayed directly into the reaction chamber through a nozzle. Thesettings on the nozzle can be adjusted to spray the aqueous H₂O₂ as aspray, mist or vapor. Any means known in the art for introducing aqueoushydrogen peroxide into the reaction chamber can be used.

If the aqueous H₂O₂ in the supply is more concentrated than desired, itcan be diluted by mixing with more water before it is sprayed into thereaction chamber using any method for mixing fluids known in the art. Inone embodiment, the dilution is accomplished by simply adding thecorrect amount of water to the aqueous H₂O₂ in the supply tank to obtainthe desired strength before turning the system on. In some suchembodiments water is provided by self-contained portable water thatwould make the system suitable for installation in a tank or ambulance.In another embodiment, aqueous hydrogen peroxide is released from theaqueous hydrogen peroxide supply through a conduit and is injected intoa mixing bowl. Water is released from a water supply through a conduitand is also injected into the same mixing bowl where it dilutes thehydrogen peroxide to the desired concentration. Methods known in the artfor mixing fluids and monitoring the concentration of hydrogen peroxidecan be used to automate the system. After the correct concentration ofaqueous hydrogen peroxide is achieved, it is introduced as a spray, mistor vapor through a nozzle into the reaction chamber where it isirradiated with UV light to form hydroxyl radicals that kill orneutralize pathogens by oxidation.

In the illustrated embodiments, an optional porous matrix 107 (FIG. 1and FIG. 2), such as metal foam, is installed in the reaction chamber toprovide additional surface area on which free radicals can react withthe pathogens. In one embodiment, the porous matrix covers the reactionchamber air outlet 109 to assure that air passes through the porousmatrix before leaving the neutralization system. The porous matrix isrecommended where large volumes of air are being decontaminated; itssize and thickness can be adjusted to accommodate large volumes of air.The embodiment illustrated in FIG. 1 or FIG. 2 has sensors 110 a, 110 bto monitor H₂O₂ levels, humidity, temperature, ultraviolet light levelsor any other parameter of interest or some combination of these. Thesensors can be located inside the reaction chamber 110 a, and outsidethe reaction chamber 110 b at a point near air outlet 109. In someembodiments the neutralization system is fully automated so thathydrogen peroxide or ozone or both are dispensed based on measurementsobtained from sensors 110 a or 110 b or both.

Although the results in Example 3 show that ozone is not requiredneutralize airborne Bacillus globii spores, it is possible that certainairborne pathogens are more effectively neutralized with the addition ofozone to hydrogen peroxide. UV, hydrogen peroxide, UV light, and ozoneare themselves antimicrobial sterilizing agents. Irradiation with highintensity, broad spectrum UV light from about 150 nm to about 300 mnm,especially from about 250 nm to about 270 μm, causes aqueous H₂O₂ andozone in water to form hydroxyl radicals (OH⁻) that are even moreeffective pathogen neutralizing agents. The various chemical reactionsand free radicals formed in a UV/H₂O₂/ozone system are shown in FIG. 5.

Destruction of airborne chemical toxins by free radical oxidation or byinteraction with UV light, ozone, and H₂O₂ or some combination, isaccomplished by embodiments of the invention and is discussed in moredetail below. Ozone can be generated by a corona discharge generator orby UV light and air, or it can be stored in a tank or reservoir. Ozonecan also be generated by ultraviolet light and air. Ozone generatorsthat are compatible with the pathogen-toxin neutralization system of thepresent invention are described Potember. The ozone supplies andgenerators are inside the reaction chamber in some embodiments.

FIG. 2. In the illustrated embodiments of the UV/H₂O₂/ozone system,ozone and aqueous hydrogen peroxide are mixed together before beingsprayed into the reaction chamber. An external aqueous hydrogen peroxideand ozone supply combination 204 is provided. Details of differentembodiments of the hydrogen peroxide and ozone supply 204 areillustrated in FIG. 3 as 204 a, and in FIG. 4 as 204 b.

FIG. 3 shows an embodiment of the UV/H₂O₂/ozone system wherein supply204 a has an aqueous H₂O₂ storage tank 301, an ozone generator 303, aninjection pump 307, a supply line 212, and conduits 311. Aqueoushydrogen peroxide in storage tank 301 is mixed with ozone supplied byozone generator 303 when the system is operational. Ozone generated byozone generator 303 passes through a conduit 311 to ozone injector 305,which injects ozone into aqueous H₂O₂ storage tank 301 to form a mixtureof aqueous H₂O₂ and ozone. The mixture thus formed passes throughconduit 311 to injection pump 307 that injects the mixture into supplyline 212, which is the conduit to reaction chamber 101. Return to FIG.2. Once the mixture is sprayed into reaction chamber 101 through nozzle205, the UV light 106 causes H₂O₂, water and ozone to form hydroxylradicals (OH⁻) 211. Ozone also forms some other highly reactiveintermediates illustrated in FIG. 5. Hydroxyl radicals, ozoneintermediates, ozone, hydrogen peroxide and UV light mix with andoxidize airborne pathogens in the incoming contaminated air and onporous matrix 107 inside reaction chamber 101, thereby neutralizing thepathogens. Return to FIG. 3. When the UV/H₂O₂/ozone system is on, someof the mixture of hydrogen peroxide, water and ozone in the supply 204 apasses through conduit 311 to recirculation pump 309, which pumps themixture through conduit 311 to ozone injector 305 so that ozone iscontinually replenished.

Another embodiment of the aqueous H₂O₂ and ozone supply 204 isillustrated in detail as 204 b in FIG. 4. In this embodiment the aqueousH₂O₂ and ozone supply 204 b is reagent-less, having both an ozonegenerator 401 and a hydrogen peroxide generator 409. Ozone generatedfrom ozone generator 401 flows through conduit 403 to ozone injector 405where it is mixed with water. Water flows from water supply 407 throughconduit 403 to ozone injector 405. In various embodiments the watersupply can be a storage tank or a line hooked up to a building supply ofwater. The water-ozone mixture flows from ozone injector 405 throughconduit 403 to the fluid inlet 411 and into hydrogen peroxide generator409. Hydrogen peroxide is generated from electricity and water. Themixture of ozone, water and hydrogen peroxide thus formed flows out ofhydrogen peroxide generator 409 through fluid outlet 412 and into supplyline 212, which is the conduit to the reaction chamber 101. The fluid inthe aqueous H₂O₂ and ozone supply in 204 a and 204 b, or variationsthereof, can be moved by fluid pumps or injectors located as neededthroughout in the system according to methods known in the art. In someembodiments ozone supply 401 and injector 405 are omitted to create aUV/hydrogen peroxide system.

Ozone generally occurs in natural settings at around 0.02 ppm (parts permillion), but it can be found as concentrated as 0.10 ppm, at whichlevel it keeps pathogens in check without being harmful to animals orman. Prolonged exposure to much higher levels of ozone may lead todiscomfort, headache, and coughing, warning humans to leave the spaceand seek better air. OSHA has stipulated that the safe allowable levelof residual ozone is 0.1 ppm for continuous exposure throughout anentire 8-hour day for 5 days a week. As soon as ozone is formed in thegenerator and introduced into the reaction chamber, it either begins todecay back into stable oxygen, or it reacts with water in the presenceof high intensity, broad spectrum UV light to form highly active,short-lived intermediates. The maximum half-life of ozone isapproximately 30 minutes. However, in practice the half-life is usuallymuch shorter due to interactions with contaminants in the air andcontact with surfaces such as walls and carpets. Exposure to ozonelevels four to five times the approved levels for short periods of timehave no adverse effects because the ozone itself decays back to oxygenrapidly. Levels of ozone from about 0.01 ppm to about 1000 ppm,especially from about 0.1 ppm to about 100 ppm can be maintained in thereaction chamber of the various embodiments of the presentneutralization systems.

The embodiment of the UV/H₂O₂/ozone system in FIG. 2 also has anoptional solid support 208 made of or coated with one or more agentsthat adsorb, trap or chemically neutralize airborne pathogens orchemical toxins or both. In some embodiments the solid support isdisposed near or next to air outlet 109. The coatings on the solidsupport can be different depending on the pathogen(s) or chemicaltoxin(s) being targeted. In the UV/H₂O₂/ozone system, a solid support208 is included that is coated with or made of ozone removal catalystsand disposed near the air outlet to capture and neutralize any unusedozone before it leaves the system. In some embodiments, more than onesolid support is included in the system, each coated with variouscompounds chosen based on their ability to trap or neutralize thetargeted pathogens, or chemical toxins or ozone.

Ozone removal catalysts known in the art include platinum-alumina watervapor catalyst (H₂O—Pt—Al₂O₃) called Dash-220, which decomposes ozone inmoist conditions. Other ozone decomposition catalysts include: CorotecCorp. NOZONE® all-aluminum canister; Hoechst Corp. NoXon polymer; acarbon supported metal oxide catalyst (MnO₂—Fe₂O₃, MnO₂); CuCl₂-coatedcarbon fibers; carbon-iron aerosol particles; alumina; and metalcatalysts such as platinum, palladium, and nickel. In one embodiment,the solid support is removable and can be changed when the catalystshave been used up. In another embodiment, the solid support itself isreusable and can be recharged with fresh ozone removal catalysts orother additives or coatings, including antibodies, before beingreintroduced into the pathogen-toxin neutralization system.

In various embodiments, the present neutralization system can beoperated in continuous or intermittent modes at a wide range of ambienttemperatures, including in air cooled by air conditioning or heated inthe winter, in desert air that is dry and hot, or very cold air, or somecombination. In some embodiments, the chamber is heated by theinstallation of heating coils that can be disposed on the outside of thechamber, or in the chamber walls. Similarly, in some embodiments thereaction chamber is cooled using any known technology; such as with acooling tower or cooling coils that remove heat from the neutralizationsystem. In some embodiments a HEPA filter is disposed upstream from theneutralization system to remove approximately 99.97% of airborneparticulate matter before contaminated air entered the neutralizationsystem. HEPA filters have an additional important use in that theyremove spores that are known to be especially difficult to neutralize incirculating air. However, HEPA filters do not capture viruses. Invarious embodiments activated carbon filters are used to removeparticulate matter; they are disposed either upstream or downstream fromthe neutralization system, or in both locations.

In some embodiments, the reaction chamber has more than one chamber airinlet or outlet or both. This permits the installation of theneutralization system at locations where several ducts converge. Inother embodiments the neutralization system is entirely self-contained.In some entirely self-contained systems, the hydrogen peroxide generatoris disposed inside the reaction chamber. The water supply is connectedto a tank. Thus, the neutralization system can be scaled down to a sizethat is portable, and suitable for use in vehicles such as militarytanks.

The present neutralization systems can also be used to clean aircirculating through air conditioning or heating systems having one ormore ducts that move and direct the circulating air. It can be installedin existing heating and air conditioning ducts by removing a section ofthe existing duct to accommodate the reaction chamber, and connectingthe reaction chamber to the existing duct at the chamber air inlet andoutlet. The various embodiments of the neutralization systems of thepresent invention are installed so that contaminated air passes into thechamber from the existing duct through the air inlet, and decontaminatedpathogen-neutralized air leaves the system through the air outlet fromwhich it passes back into the existing duct for recirculation. To assurethat the contaminated air enters and passes through the neutralizationsystem, the chamber air inlet and outlet are adapted to fit the existingducts using methods known in the art so that no air is allowed to bypassthe system. In one embodiment, the chamber air inlet/outlet is adaptedto fit an existing building air duct using a flange, with a rubberO-ring between the chamber wall and the flange to prevent air leaks.

FIG. 6 illustrates the embodiment the UV/H₂O₂/ozone system that was usedin Example 2. Ozone supply 603 is an ozone gas generator connected toozone conduit 603 a, which connects to ozone-aqueous H₂O₂ mixing chamber612 at ozone conduit opening 612 a. Downstream from the ozone generatoris an aqueous hydrogen peroxide supply 604 that releases a stream ofaqueous hydrogen peroxide into aqueous hydrogen peroxide conduit 613. Asthe aqueous hydrogen peroxide stream flows past ozone conduit opening612 a, it creates a vacuum that helps to pull the ozone exiting theozone generator 603 through ozone conduit 603 a into the ozone-aqueousH₂O₂ mixing chamber 612 at conduit opening 612 a, where a mixture ofozone and aqueous H₂O₂ is formed. After the ozone/aqueous hydrogenperoxide mixture is formed, it is sprayed through nozzle 605 intoreaction chamber 101. It is then irradiated with UV light to formhydroxyl radicals and other reactive intermediates that kill pathogens(and neutralize chemical toxins).

2. Methods for Neutralizing Pathogens or Chemical Toxins

Although the steps of the method for neutralizing pathogens using theneutralization system of the present invention are described in aparticular order below, in other embodiments the steps may occur in adifferent order or overlapping in time. An embodiment of a method ofneutralizing airborne pathogens or chemical toxins in ventilated airinvolves the steps of:

-   -   a. introducing air contaminated with pathogens or chemical        toxins or both into a flow-through reaction chamber;    -   b. introducing aqueous hydrogen peroxide into the flow-through        reaction chamber to form a mixture of contaminated air and        aqueous hydrogen peroxide inside the reaction chamber;    -   c. irradiating the mixture with ultraviolet light thereby        neutralizing the airborne pathogens or chemical toxins or both        to create decontaminated air; and    -   d. releasing the decontaminated air from the reaction chamber.

In some embodiments there is an additional step before step c ofintroducing ozone into the reaction chamber to form a mixture ofcontaminated air, aqueous hydrogen peroxide and ozone. This mixture isthen irradiated to neutralize airborne pathogens or chemical toxins orboth. In other embodiments, aqueous hydrogen peroxide is mixed withozone before being introduced into the reaction chamber. Thus a mixtureof contaminated air, aqueous hydrogen peroxide and ozone is formed instep b, and this mixture is irradiated in step c. In some embodiments, aconcentration of hydrogen peroxide is maintained in the flow throughreaction chamber at a level in a range from about 1% to about 50%,especially from about 1% to about 25%. In embodiments where ozone isintroduced, a concentration of ozone in the reaction chamber ismaintained at a level in a range from about 0.01 ppm to about 100 ppm,especially from 0.1 ppm to about 100 ppm.

3. Advantages of the UV/H₂O₂ and the UV/H₂O₂/Ozone NeutralizationSystems

Advantages of the illustrated embodiments of the UV/H₂O₂ and theUV/H₂O₂/ozone neutralization systems include the following:

-   -   The neutralization systems neutralize airborne pathogens or        chemical toxins in real time in large volumes of moving air;    -   The neutralization systems can be installed in conjunction with        other air pathogen-toxin neutralization technologies such as        installing the neutralization system at a location that receives        air that has been passed through a pre-existing HEPA filter        system.    -   The neutralization systems are activated and operated        electrically.    -   The major components of the neutralization systems are        commercially available.    -   The neutralization systems can be reagent-less by using a        hydrogen peroxide or an ozone generator, or both. Hydrogen        peroxide can be generated from water using electricity. Water        can be provided from a portable supply or from a building's        low-pressure supply. Ozone is generated from water and molecular        oxygen in the room air.    -   Stable byproducts are created UV irradiation generates hydroxyl        ions that are extremely short-lived. If ozone is used, a solid        support coated with ozone removal catalysts prevents unused        ozone from exiting the reaction chamber. If any residual aqueous        hydrogen peroxide exits the system in decontaminated air, it can        be captured using, for example, a dehumidifier downstream from        the air outlet of the reaction chamber or any other method for        trapping or neutralizing hydrogen peroxide. In another example,        additional UV lights could be placed outside the system near the        air outlet to convert escaping hydrogen peroxide to very        short-lived hydroxyl radicals and water. Residual hydrogen        peroxide is expected to be small enough, particularly with        concentrations of aqueous hydrogen peroxide below about 25%.    -   The neutralization system requires minimum maintenance.    -   One or more UV lights can be operated in tandem or independently        with the ozone generator or the hydrogen peroxide generator.    -   Commercially available hydrogen peroxide, humidity, particle        sampling, ozone, and UV light sensors allow the neutralization        systems to be microprocessor controlled and continually        balanced.    -   Some embodiments include an open-pore metal foam support in the        reaction chamber that produces a beneficial low-pressure drop        across the neutralization system. The porous matrix also        provides the medium in which concentrations of hydroxyl        radicals, hydrogen peroxide, ozone, and ozone intermediates        diffuse and react with airborne pathogens or chemical toxins.    -   Several pathogen- and chemical toxin-neutralization approaches        can be combined by the present invention: the UV/H₂O₂ system        combines H₂O₂, UV and hydroxyl radical sterilization; the        UV/H₂O₂/ozone system combines sterilization by H₂O₂, UV, ozone,        hydroxyl radicals and other highly reactive ozone intermediates.    -   The system is flexible. UV light plus hydrogen peroxide or ozone        or a mixture of both at various concentrations can be chosen        based on the targeted pathogens and chemical toxins. The use of        ozone may not always be needed. Also the solid support and        coatings thereon can be selected or changed as needed to adsorb        or neutralize various combinations of airborne pathogens and        chemicals.

Both the UV/H₂O₂ and the UV/H₂O₂/ozone neutralization systems can beself-contained. For example, in one embodiment, the UV/H₂O₂ systemincludes a hydrogen peroxide generator or reservoir and a portablere-circulating water supply that permits water to be reused. Variousembodiments of the neutralization systems can be made in different sizesthat can be adapted for installation in cars, tanks, aircraft, etc. Theinstallation of the present neutralization systems in ventilated airhandling system is simple. Installation can be accomplished by cuttingan opening in an existing air duct in a structure and removing a sectionof it to accommodate system. The actual system is then installed in theexisting duct by connecting the chamber air inlet and chamber air outletof the system in sealing relation to the existing duct so thatpathogen-contaminated air is blown into the reaction chamber through thechamber air inlet, and decontaminated air leaves the system through thechamber air outlet. The illustrated embodiments require electricity, andsome embodiments require a hook up to a water supply.

4. Details of Structural Components

4.1 Hydrogen Peroxide and Ozone Supply

The results set forth in Examples 2 and 3 show that levels of about15-25% H₂O₂ in water reduced airborne Bacillus globii spores toundetectable levels in real time as they passed through the reactionchamber. Fifteen percent H₂O₂ was chosen because it is safe to handlewithout burning the skin. The optimum concentration of H₂O₂ may varydepending on the ambient temperature and the targeted pathogens orchemical toxins. H₂O₂ for use in the present system can be generatedchemically or electrically using any method known in the art, includingthose listed in Table 2. TABLE 2 Chemical generation of H₂O₂:Catalyst/anthroquinone O₂ + H₂ = H₂O₂ Commercial preparation Electricalgeneration of H₂O₂: H₂O + Electricity = H₂O₂ Electrochemical generationFree radical (OH⁻) generating chemical Reactions based on H₂O₂ H₂O₂ +Quaternary ammonium salts = H₂O + OH⁻ Chemical generation H₂O + H₂O₂ =H₂O + OH⁻ hydroxyl radicals Catalyst H₂O + H₂O₂ = H₂O + OH⁻ hydroxylradicals UV light H₂O + H₂O₂ = H₂O+ OH⁻ hydroxyl radicals Heat

Use of a hydrogen peroxide generator has the advantage that it isreagent-less, thus eliminating the need to store or transport chemicals.The use of an H₂O₂ generator permits the design of a lighterneutralization system that can be easily transported into remotelocations where limited resources are available. Only water andelectricity need to be supplied. Thus, the UV/H₂O₂ neutralization systemcan be scaled down to a size that is portable, and suitable for use invehicles such as military tanks.

Electrochemical generation of H₂O₂ is accomplished by passing water overa stacked electrode bank. One such electrode bank is made of parallelTitanium-metal plates coated with titanium oxide (TiO₂) doped with4-mole % nibidium (n) or tantalum (t) in the +4 oxidation state. Thisoxide coating is heavily n-doped which makes the system extremelycorrosion resistant at the potential (+2.74 V) required to generate theradical (OH⁻). This method has demonstrated hydroxyl radical generationat 7.5-19 moles/kilowatts per hour when operated in a continuous flowmode for other applications. The hydrogen peroxide generator releaseshydrogen peroxide on demand to maintain desired levels inside thereaction chamber. There is no limit on the concentration of hydrogenperoxide that can be used in the present systems, however, amountsranging from about 1% to about 50%, or more typically from about 3% toabout 25%, are sufficient to neutralize most airborne pathogens orchemical toxins or combinations thereof. Routine experimentation asdescribed in the examples under controlled conditions with known agents,biological or chemical, or combinations thereof will demonstrate theoptimum levels of H₂O₂ or ozone. For some uses, the level of aqueoushydrogen peroxide in the system may be sufficient at less than 1%. Thelevel of H₂O₂ supplied to the system can be monitored by one or moresensors. Any method for producing H₂O₂ can be used in the presentinvention.

To optimize pathogen or chemical toxin neutralization, the pH of thewater introduced into the system can be adjusted. Routineexperimentation will determine the optimum pH for neutralizing variouspathogens, chemical toxins or combinations thereof. Where neutralizationof a given pathogen is enhanced by acidic pH, the water can be treatedwith acetic acid to obtain the desired pH before it is sprayed into theneutralization system. Alternatively, a basic pH can be obtained wherebeneficial. In some embodiments, a coating is applied to the porousmatrix or solid support that adjusts the pH to a level that optimizesneutralization of the targeted pathogen or chemical toxin.

4.2 Broad Spectrum UV Light Source

UV light from about 100 nm to about 400 nm causes hydrogen peroxide toform highly active free radical intermediates that in turn react withand destroy pathogens. An UV wavelength of about 250 nm to about 270 wasused in the examples. UV radiation is itself intrinsically toxic to somepathogens, causing radiation damage to the pathogen's DNA so that itcannot reproduce. High levels of UV radiation are considered lethal formost microorganisms, including bacteria, fungal spores, viruses,protozoa, nematode eggs and algae. That part of the UV light spectrumknown to kill or neutralize most pathogens is between 100-400 nm, whichis just shorter than the wavelengths of visible light. However, UVsterilization is more effective on surfaces than on airborne pathogens.Bacteria are the easiest pathogens to neutralize; viruses and spores aremore resistant. Spores of the Bacillus species possess a thick proteincoat that consists of an electron-dense outer coat layer and alamella-like inner coat layer. This coating reduces the effect of UVirradiation on the pathogen's DNA.

Incandescent, quartz or mercury vapor lamps are suitable for use in thepresent pathogen-toxin neutralization systems. UV light can becontinuous or pulsed, and high intensity UV lights are preferred. In aflashing UV light, each high power flash or pulse lasts only a fewhundred millionths of a second. A typical flash of UV light lasts fromabout 1 to about one millionth of a second, and has a flash repetitionrate from about 1 to 10 flashes per second. The duration, wavelength,and intensity of the UV light can be adjusted to optimize the effect onvarious pathogens. Flash frequency can vary from 1-1000 per second asdetermined by experimentation.

The use of UV light is the easiest way to convert H₂O₂ to hydroxylradicals, and ozone to hydroxyl radicals and other reactiveintermediates, however any method known in the art can be incorporatedinto the present system in addition to or in place of UV lights,including the use of heat and catalysts.

4.3 Porous Matrix Composition

In some embodiments a porous matrix disposed inside the reaction chamberprovides an increased surface area on which the free radicals, ozoneintermediates, ozone and hydrogen peroxide contact and react withairborne pathogens in a micro-solvent environment. The solvent is waterthat condenses on the pathogens. In the examples, the porous matrix usedwas a DUCOCEL® aluminum metal foam having a pore size of 40 PPI (poresper square inch) and 8% density. DUCOCEL® is used to mix rocket fuelsprior to ignition. It has a reticulated structure of open,duodecahedronal-shaped cells connected by continuous, solid metalligaments. The matrix is completely repeatable, regular and uniformthroughout the material. DUCOCEL® is a rigid, highly porous andpermeable structure with a controlled density of metal per unit volumethat does not reduce the flow rate of incoming air. It is available in6101 and A356 aluminum alloys and in vitreous or glassy carbon, othermetals, ceramics and composite materials. Density is continuouslyvariable from 3-12 percent. No degradation of DUCOCEL® was seen afterseveral months of use. The DUCOCEL® matrix adds a large surface area onwhich the ozone intermediates and pathogens interact. The matrix doesnot noticeably impede the airflow. In some embodiments, the porousmatrix is removable and reusable. In various embodiments, the volume,thickness and density of the porous matrix can be varied depending onthe volume of contaminated air being passed through the neutralizationsystem and the size of the chamber air outlet. Porous matrices from 1inch to 3 inches thick have been tested and do not impede air flow.

Increasing the air velocity serves to mix the contaminated incoming airwith the water vapor containing highly reactive free radicals. In someembodiments where very large volumes of air are being decontaminated,one or more fans are added to the system to further assist mixingcontaminated air with the free radicals, ozone, hydrogen peroxide andwater. In embodiment for large-scale applications, the airflow isdramatically increased by increasing the cross sectional area of theporous metal structure and adjusting the size of the air inlets and airoutlets.

Any solid porous matrix can be used that increases surface area withoutblocking air outflow from the neutralization system or inhibiting theformation of the highly reactive ozone intermediates. In someembodiments, metal foams that have antibacterial activity are used, suchas copper and silver. Porous matrices of plastics, polymers, particleballs, thread or ceramics or some combination thereof is also used invarious embodiments. In some embodiments, the porous matrix is coatedwith one or more non-volatile antibacterial, antiviral and antisporeagents that increase pathogen-toxin adsorption and/or neutralization.This may be advantageous where a pathogen is highly resistant toneutralization. In various embodiments the matrix or one or more solidsupports is coated with agents that trap and/or neutralize chemicalweapons. In some embodiments the coatings are biological or chemical orboth, and include compounds such as antibodies directed to bacterialcell walls, DNA, bacterial toxins, viruses, prions, etc. Routineexperimentation will determine which additives are the most effective,and this will vary depending on the targeted pathogens or toxins.Similarly, coatings that adsorb or neutralize chemical toxins can be putonto one or more solid supports in the various systems of the presentinvention.

4.4 Use of Surfactants, Ultrasound, and Microwaves

To increase the effectiveness of ozone, hydrogen peroxide and freeradicals on airborne pathogens, especially spores, nontoxic surfactants(soap molecules) are pre-mixed with the water and sprayed into thereaction chamber in some embodiments. It is expected that thesurfactants increase the contact time between ozone and ozone freeradicals and pathogens, thus facilitating pathogen-toxin neutralization.One or more nontoxic surfactants known in the art, or mixtures thereof,can be used in various embodiments.

Any means of disrupting or fracturing the pathogens, including thecoating protecting spores, increases the effectiveness of neutralizationin the embodiments. It is expected that the disruption facilitates theinteraction of the highly active free-radicals, hydrogen peroxide, ozoneintermediates, free ozone and UV light to interact with the pathogen.Microwaves and/or ultrasound may help to break down the spore coating tomake the spores more susceptible to neutralization. Plasma DC glowdischarge has been shown to be an effective sterilization method formedical devices on its own. The principle sterilization using plasma DCglow discharge is intense UV radiation in the 160-240 nm range.Therefore in some embodiments, the neutralization system furtherincludes a plasma DC glow discharge UV tube, a microwave generator, oran ultrasound generator or some combination. In alternative embodiments,contaminated air is treated before it enters the system by placing ameans for producing microwave irradiation, plasma DC glow discharge,and/or ultrasound upstream near the chamber air inlet.

In some embodiments, aqueous hydrogen peroxide and contaminated air aremixed together, with or without ozone, in a vortex mixer that isirradiated with UV light before being sprayed into the reaction chamber,where it is optionally irradiated again with UV light. In an embodiment,ozone is also added to aqueous hydrogen peroxide and contaminated air.The components are introduced through separate lines into the mixer. Insome embodiments aqueous hydrogen peroxide and ozone are premixed beforebeing introduced into the vortex mixer where they are further mixed withincoming contaminated air mixture.

4.5 Chemical Toxin Neutralization

Some embodiments of the UV/H₂O₂ and the UV/H₂O₂/ozone systems are notonly useful in neutralizing airborne bacteria, they also destroyairborne chemical weapons by converting the chemical toxins to benignforms, primarily by oxidation. Hydroxyl ions and ozone intermediates arevery powerful oxidants that react with organic molecules to form carbondioxide and water. Chemicals that are known to be oxidized toenvironmentally benign forms by hydrogen peroxide and hydroxyl ionsinclude: organic compounds, chlorinated VOCs, mercaptans, nitriles,aldehydes, alcohols, amines, metals, alkylboranes, azo-compounds,cyanides, phenols, sulfides, chromium and some inorganics. O'Brien &Gere Engineers, Inc. Innovative Engineering Technologies for HazardousWaste Remediation, New York: Van Nostrand Reinold; 1995; Clarin et al.UV radiation by itself degrades polychlorinated biphenyls, dioxins,polyaromatic compounds and breaks many covalent bonds. Clarin, et al. Italso enhances chemical oxidation, though the mechanism is uncertain. Onetheory is that organic compounds absorb light energy at visible or UVwavelengths and as a result are easier to destroy.

It has been reported that UV, ozone and peroxide treatment ofcontaminated water destroys halogenated solvents, phenol,pentachlorophenol, pesticides, polychlorinated biphenyls, explosives,BTEX, MTBE and many other organic compounds. Clarin, et al. Table 4contains a list of chemical agents. To the extent that any of thecompounds named above and in Table 4 become airborne and are oxidized toa benign state by hydroxyl radicals, hydrogen peroxide, UV light orozone, the embodiments of the present neutralization systems will beeffective. Routine experimentation will determine the optimum levels ofhydrogen peroxide, ozone, or combinations thereof for neutralizing eachpathogen or chemical agent. Some embodiments of the neutralizationsystems of the present invention include one or more solid supports thatare coated with biological or chemical agents that trap or neutralizeairborne chemical weapons. TABLE 4 CHEMICAL AGENTS AbrinMethyldichloroarsine (MD) Adamsite (DM) Mustard Gas (H) (Sulfur Agent 15Mustard) Ammonia Mustard/Lewisite (HL) Arsenic Mustard/T Arsine (SA)Nitrogen Mustard (HN-1, Benzene HN-2, HN-3) Bromobenzylcyanide CANitrogen Oxide (NO) BZ Paraquat Cannabinoids Perflurorisobutylene (PHIB)Chlorine (CL) Phenodichloroarsine (PD) Chloroacetophenone (CN)Phenothiazines Chloropicrin (PS) Phosgene (CG) CNB (CN in Benzene andPhosgene Oxime (CX) Carbon Tetrachloride) Phosphine CNC (CN inChloroform) Potassium Cyanide (KCN) CNS (CN and Chloropicrin RedPhosphorous (RP) in Chloroform) Ricin CR Sarin (GB) CS Sesqui MustardCyanogen Chloride (CK) Sodium Cyanide (NaCN) Cyclohexyl Sarin (GF) Soman(GD) Diphenylchloroarsine (DA) Sulfur Mustard (H) (MustardDiphenylcyanoarsine (DC) Gas) Diphosgene (DP) Sulfur Trioxide- DistilledMustard (HID) Chlorosulfonic Acid (FS) Ethyldichloroarsine (ED) Tabun(GA) Fentanyls and Other Opioids Teflon and Hydrofluoric AcidPerflurorisobutylene (PHIB) Hydrogen Chloride Thallium Hydrogen Cyanide(AC) VX Lewisite (L, L-1, L-2, L-3) LSD

Embodiments of the UV/H₂O₂ system and the UV/H₂O₂/ozone systemneutralize pathogens and other toxins in several ways. The initialelements themselves (UV, ozone and hydrogen peroxide) have intrinsicsterilizing potential, and the hydroxyl radicals and ozone intermediatesformed upon UV irradiation are yet more reactive than the parentcompounds. Ozone, its intermediates and hydroxyl radicals react withorganic molecules in many ways, including inserting an oxygen into abenzene ring, breaking double bonds to form aldehydes and ketones, andreacting with alcohol to form organic acids. LaGrega, M. et al.,Hazardous Waste Management, New York: McGraw-Hill, Inc. For example, itis known that deadly cyanide (NaCN) is oxidized by ozone to a saferproduct NaCNO as follows: O₃ NaCN=>NaCNO+O₂.

Embodiments of the neutralization systems described herein are adaptedto be portable so that they fit into trucks that transport food toprevent pathogens or chemical toxins in the air from contaminating thefood.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made to the inventionswithout departing from the broader spirit and scope of the invention.The efficacy of some embodiments is described in further detail, in thefollowing non-limiting examples.

5.0 EXAMPLES 5.1 Example 1 Experimental Set Up

A. The Air Sampler

The New Brunswick Scientific Microbiological Air Sampler Series STA-204(a slit sampler) was used to test performance of the embodiments. Totest the extent of contamination in incoming air just before it entersthe neutralization system, samples were passed over the system inletplate. Samples of outgoing air just after leaving the system were passedover the system outlet plate. The slit sampler works by drawing a knowntotal volume of air by vacuum through a slit opening. A pressure dropthat occurs across the slit causes the air with its entrainedcontaminants to accelerate to a higher velocity. The airborne pathogencontaminants, because of their heavier mass, are impacted onto thesurface of a sterile petri dish placed on a rotating, timed turntable.Only the small area of surface of the agar that is disposed just belowthe slit is exposed to the contaminated air. Thus as the dish rotates,different sectors of agar are exposed. A sample time of thirty minuteswas selected for all experiments. The sampler was set so that theduration of the experiment is equivalent to one complete revolution ofthe petri plate. When the sample time has elapsed, no further air sampleis taken. A particle distribution guide can be used to estimate the timeat which contamination occurred. The guide is a mylar disk that isdivided into thirty segments by lines that emanate from near the centerto a marker circle near the outer edge. The bottom of the petri dish ismarked with a line to indicate the position of the dish at time zero.This makes it easy to line up the particle guide. In the examples,samples of incoming air taken continuously were impacted onto the systemair inlet plate, and samples of outgoing air were impacted onto theSystem air outlet plate during each thirty minute experiment. Theexperiments described in the examples using the UV/H₂O₂/ozone system(Example 2) and the UV/H₂O₂ system (Example 3) were conducted in thesame way, except that the neutralization system in Example 2 includedozone while the system in Example 3 did not.

In the examples, the systems included a fan to help pull air through thesystem. The fan was turned on in all experiments. A modified residentialair handler was used as the reaction chamber in the examples, that has anominal capacity of 1000 cubic feet per meter (cfm) through an 18 by20.5 inch opening. The air inlet was restricted to the size of a 6-inchround duct in the test model, and 2.5×3.25 inch foam metal DUCOCEL®matrix covered the air outlet, which had the same dimension. The airvolume passing through the foam metal was only 50 cfm. The air velocitythrough system is about 78 fpm (normally ˜500 cfm), while the velocitythrough foam metal is ˜1616 cfm. This occurs because air accelerates asit passes through the system. The smaller, restricted air inlet servesto dramatically increase the air velocity that mixes intake air withpathogens and water spray containing free radical species.

A CD-5 GENESIS™ corona discharge ozone generator 603 made by DelIndustries, Inc. with maximum output of 5 g/hr was disposed outside thereaction chamber. The UV light source 106 consisted of two BioAire-UVLights Model BUV 24DE Double Ended Fixtures. The brand of light is notcritical; however, more powerful UV lights are preferred. New pulsed UVlight sources that are extremely powerful are available and may be usedin the present invention. The size of the reaction chamber was 45 incheslength×21 inches height×23 inches diameter. The air inlet 202 and airoutlet 209 were sized to fit tightly onto a commercially availableflexible duct, to which duct they were connected with a flange or collarand a rubber seal. This tight connection prevents air loss and assuresthat air leaving the air duct had passed through the UV/ozoneneutralization system.

A porous metal foam 107 matrix was made of DUCOCEL® aluminum metal foamhaving a density of 8% and 40 PPI was used. Several sheets of the foamwere cut and stacked until the stack measured 3.5 inches long and twoinches in height and thickness. The matrix was held in place byrestriction plates and was installed so that it was just in front of andcovered the chamber air outlet 109 so that the air that enters thesystem passes through the matrix before exiting the neutralizationsystem.

Room air entered the neutralization system through the chamber airinlet. The humidity of the disinfected air leaving the reaction chambervaried from about to 65 percent, and the temperature was roomtemperature. The ozone generator and the UV light source were operatedin tandem throughout the experiments, and the neutralization system wasoperated in a continuous mode with the fan on during the experiments.

The nozzles used put out approximately 29 ml of fluid per minute on thesurface of the metal matrix material. Air exiting the system has ahumidity of about 55-60%. Bacillus globii spores were cultured in thelaboratory using standard techniques well known in the art until theyattained a cell density of about 5.3×10⁹ CFU/ml.

B. Introduction of Airborne Pathogens into the Neutralization System.

In each experiment in Examples 2 and 3, Bacillus globii spores wereintroduced into the reaction chamber using the MICRO MIST™ nebulizer.Bacillus globii spores were cultured in the laboratory using standardtechniques well known in the art until they attained a cell density ofabout 5.3×10⁹ CFU/ml. About 3-6 ml of these cultured bacterial spores(about 3-6×10⁹ spores) was introduced into the reaction chamber in eachTest below. No spores were introduced in the control experiments.

5.2 Example 2 The UV/H₂O₂/Ozone System

The parameters of the experiment are set forth in Table 3 below. TABLE 3Parameter Name Parameter Setting Airflow Rate 50 CFM Water flow tonozzle 0.46 GPH (1.74 ml/hr) Injector Model Number 684 O₃ ConcentrationAs attained using injector and flow rate specified H₂O₂ Concentration25% # of UV lights 6 Position of UV lights 8″ from media pad Number ofNozzles 1 Model of Nozzle 684 Position of Nozzle 2.5″ from media padMedia Pad Size 1.5 × 3.25 Velocity Through media pad 1,600 FPM

Control: Room air was drawn through an inactive neutralization systemwith all components switched off before any spores were intentionallyintroduced. No hydrogen peroxide or ozone was introduced, and the UVlight was off. The system inlet plate was exposed to incoming room airbefore it entered the reaction chamber 101, and the system outlet platewas exposed to outgoing air that had passed through the reaction chamber101 of the inactivated neutralization system. After a thirty minuteexposure, the system inlet and outlet plates were collected and culturedfor 24 hours at 37 degrees centigrade. Fourteen colonies were observedon the system inlet plate FIG. 7A, but no colonies were observed on thesystem outlet plate FIG. 7B. The few colonies on the air inlet plateindicated that the air inlet was not properly cleaned from an earlierexperiment, but this did not affect the results of the experiments. Theabsence of colonies on the system outlet plate shows that there are nobacteria in the reaction chamber 101.

Test 1: Bacillus globii spores were introduced into the reaction chamberair inlet 102 with all systems off (no hydrogen peroxide, no ozone, UVlight off). After a thirty minute exposure, the system inlet and outletplates were collected and cultured for 24 hours at 37 degrees C. Boththe system inlet and system outlet plates were overgrown with bacteria,such that the CFU were too numerous to count as shown in FIGS. 7C and7D.

Test 2: Bacillus globii spores were introduced into the reaction chamberair inlet with the UV/H₂O₂/ozone system fully activated (aqueous H₂O₂on, Ozone On, UV On). After a thirty minute exposure, the system inletand outlet plates were collected and cultured for 24 hours at 37 degreesC. As expected, the system inlet plate was overgrown with bacteria withCFU too numerous to count. (FIG. 7E). By contrast, no CFU were countedon the system outlet plate (FIG. 7F). A large excess of airborneBacillus globii spores deliberately introduced in high numbers andpassed through the neutralization system in real time, was thus reducedto undetectable levels by the UV/H₂O₂/ozone system.

5.3 Example 3 The UV/H₂O₂System

The UV/H₂O₂ system used in Example 3 is the same as in FIG. 6, exceptthat the ozone generator was turned off.

Control: As a control, room air was drawn through an inactiveneutralization system with all components switched off. No hydrogenperoxide was introduced and the UV light was off. The system inlet platewas exposed to incoming room air before it entered the reaction chamber101, and the system outlet plate was exposed to outgoing air that hadpassed through the reaction chamber 101 of the inactivatedneutralization system. After a thirty minute exposure, the system inletand outlet plates were collected and cultured for 24 hours at 37 degreesC. Fifty-one colonies were counted on the System Inlet Dish. No colonieswere observed on the system outlet plate, FIGS. 8A and 8B. The absenceof colonies on the system outlet plate shows that there are no bacteriain the reaction chamber 101.

Test 1: Bacillus globii spores were introduced into the reaction chamberair inlet 102 with all systems off (no hydrogen peroxide, UV light off.)After a thirty minute exposure, the system inlet and outlet plates werecollected and cultured for 24 hours at 37 degrees C. Both the systeminlet and system outlet plates were overgrown with bacteria, such thatthe CFU were too numerous to count. FIGS. 8C and 8D.

Test 2: Bacillus globii spores were introduced into the reaction chamberair inlet 102 with the UV/H₂O₂ system fully activated (aqueous H₂O₂ on,UV On). After a thirty minute exposure, the system inlet and outletplates were collected and cultured for 24 hours at 37 degrees C. The CFUon the system inlet plate were too numerous to count (FIG. 8E). Bycontrast, no CFU were counted on the system outlet plate (FIG. 8F). Thelarge excess of airborne Bacillus globii spores deliberately introducedin high numbers and passed through the neutralization system in realtime, were reduced to undetectable levels by 15% UV/H₂O₂ system evenwithout ozone.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

1. A system for neutralizing airborne pathogens, comprising: A. aflow-through reaction chamber having:
 1. a chamber air inlet at a firstend of the reaction chamber to admit air contaminated with pathogens,and
 2. a chamber air outlet at a second end of the reaction chamber torelease decontaminated air, and defining between the air inlet and airoutlet a passageway, B. a supply of aqueous hydrogen peroxide connectedto a conduit for introducing aqueous hydrogen peroxide into the reactionchamber, and C. an ultraviolet light source for introducing UV lightinto the reaction chamber.
 2. The system as in claim 1, wherein thesupply of aqueous hydrogen peroxide is a hydrogen peroxide generatorconnected to a water supply and a source of electricity.
 3. The systemas in claim 1, wherein the supply of aqueous hydrogen peroxide is areservoir of aqueous hydrogen peroxide.
 4. The system as in claim 1,wherein the conduit is a nozzle disposed inside the reaction chamber. 5.The system as in claim 1, wherein the reaction chamber further comprisesa porous matrix.
 6. The system as in claim 5, wherein the porous matrixis metal foam.
 7. The system as in claim 6, wherein the metal isselected from the group comprising aluminum, copper, silver, and oxidesthereof.
 8. The system as in claim 6, wherein the metal foam is aluminumfoam.
 9. The system as in claim 5, wherein the porous matrix isremovable.
 10. The system as in claim 1, further comprising a microwavegenerator to introduce microwaves into the reaction chamber.
 11. Thesystem as in claim 1, further comprising an ultrasonic wave generator tointroduce ultrasonic waves into the reaction chamber.
 12. The system asin claim 1, further comprising an ozone supply for introducing ozoneinto the reaction chamber.
 13. The system as in claim 12, wherein theozone supply is an ozone generator.
 14. The system as in claim 12,wherein the ozone supply is a reservoir that contains ozone.
 15. Thesystem of claim 12, further comprising a mixing chamber for mixing ozoneand aqueous hydrogen peroxide.
 16. The system of claim 1, wherein thereaction chamber further comprises a solid support.
 17. The system ofclaim 16, wherein the solid support comprises ozone removal catalysts.18. The system of claim 16, wherein the solid support comprisescompounds that adsorb or neutralize pathogens.
 19. The system of claim16, wherein the solid support comprises compounds that adsorb orneutralize chemical toxins.
 20. The system of claim 19, wherein thesolid support comprises ozone removal catalysts.
 21. The system of claim17, wherein the ozone removal catalyst is a member selected from thegroup comprising all-aluminum catalysts, a carbon supported metal oxidecatalyst, CuCl₂-coated carbon fibers, carbon-iron aerosol particles,alumina, platinum, palladium, and nickel.
 22. The system of claim 13,wherein the ozone generator is a corona discharge generator.
 23. Thesystem as in claim 1, configured for operation in a continuous mode. 24.The system as in claim 1, configured to be activated upon demand. 25.The system of claim 1, further comprising a fan to move air through thepassageway.
 26. The system of claim 1, wherein an amount of hydrogenperoxide in the reaction chamber is controlled by sensors.
 27. Thesystem as in claim 1, wherein the ultraviolet light source emits highintensity UV light.
 28. The system as in claim 27, wherein theultraviolet light source emits UV light having a wavelength in a rangefrom about 250 nanometers to about 300 nanometers.
 29. The system ofclaim 1, wherein a concentration of hydrogen peroxide in the aqueoushydrogen peroxide supply is from about 1% to about 50%.
 30. The systemas in claim 1, wherein a concentration of hydrogen peroxide in theaqueous hydrogen peroxide supply is from about 1% to about 25%.
 31. Amethod of neutralizing airborne pathogens comprising:
 1. introducing aircontaminated with pathogens into a flow-through reaction chamber; 2.introducing aqueous hydrogen peroxide into the flow-through reactionchamber to form a mixture of contaminated air and aqueous hydrogenperoxide inside the reaction chamber;
 3. irradiating the mixture withultraviolet light thereby neutralizing the airborne pathogens to createdecontaminated air; and
 4. releasing the decontaminated air from thereaction chamber.
 32. The method of claim 31, further comprising theadditional step before step 3 of introducing ozone into the reactionchamber forming a mixture of contaminated air, aqueous hydrogen peroxideand ozone.
 33. The method of claim 31, step 2 further comprising mixingthe aqueous hydrogen peroxide with ozone before introducing the aqueoushydrogen peroxide to form a mixture of contaminated air, aqueoushydrogen peroxide and ozone.
 34. The method of claim 31, step 2 furthercomprising introducing the aqueous hydrogen peroxide into the reactionchamber through a nozzle disposed in the reaction chamber, to form atleast one of a spray, mist or vapor.
 35. The method as in claim 31, step2 further comprising maintaining a concentration of hydrogen peroxide inthe flow through reaction chamber at a level in a range from about 1% toabout 50%.
 36. The system as in claim 31, step 2 further comprisingmaintaining a concentration of hydrogen peroxide in the flow-throughreaction chamber at a level in a range from about 1% to about 25%. 37.The method as in claim 32, step 2 further comprising maintaining aconcentration of ozone in the reaction chamber at a level in a rangefrom about 0.01 ppm to about 100 ppm.
 38. A method of neutralizingairborne chemical toxins comprising:
 1. introducing air contaminatedwith chemical toxins into a flow-through reaction chamber; 2.introducing aqueous hydrogen peroxide into the flow-through reactionchamber to form a mixture of contaminated air and aqueous hydrogenperoxide inside the reaction chamber;
 3. irradiating the mixture withultraviolet light thereby neutralizing the airborne chemical toxins tocreate decontaminated air; and
 4. releasing the decontaminated air fromthe reaction chamber.
 39. The method of claim 38, further comprising theadditional step before step 3 of introducing ozone into the reactionchamber to form a mixture of contaminated air, aqueous hydrogen peroxideand ozone.
 40. The method of claim 38, step 2 further comprising mixingthe aqueous hydrogen peroxide with ozone before introducing the aqueoushydrogen peroxide to form a mixture of contaminated air, aqueoushydrogen peroxide and ozone.
 41. The method of claim 38, step 2 furthercomprising introducing the aqueous hydrogen peroxide into the reactionchamber through a nozzle to form at least one of a spray, mist or vapor.42. The method as in claim 38, step 2 further comprising maintaining aconcentration of hydrogen peroxide in the flow through reaction chamberat a level in a range from about 1% to about 50%.
 43. The system as inclaim 38, step 2 further comprising maintaining a concentration ofhydrogen peroxide in the flow-through reaction chamber at a level in arange from about 1% to about 25%.
 44. The method as in claim 32 or claim33, step 2 further comprising maintaining a concentration of ozone inthe reaction chamber at a level in a range from about 0.01 ppm to about1000 ppm.
 45. The method as in claim 32 or claim 33, step 2 furthercomprising maintaining a concentration of ozone in the reaction chamberat a level in a range from about 0.01 ppm to about 1000 ppm.
 46. Asystem for neutralizing airborne pathogens and chemical toxins,comprising: A. a flow-through reaction chamber having:
 1. a chamber airinlet at a first end of the reaction chamber to admit air contaminatedwith pathogens, and
 3. a chamber air outlet at a second end of thereaction chamber to release decontaminated air, and defining between theair inlet and air outlet a passageway, B. a supply of aqueous hydrogenperoxide connected to a conduit for introducing aqueous hydrogenperoxide into the reaction chamber, and C. a means for convertingaqueous hydrogen peroxide to hydroxyl radicals.
 47. The system as inclaim 46, wherein the means for converting aqueous hydrogen peroxideinto hydroxyl radicals is heat.
 48. The system as in claim 46, whereinthe means for converting aqueous hydrogen peroxide into hydroxylradicals is electricity.